In intestinal amoebiasis, motile Entamoeba histolytica trophozoites with ingested erythrocytes should be identifiable in stool or mucosal scrapings. Finding E. histolytica cysts is not sufficient for the diagnosis. The diagnosis of amoebic liver abscess is confirmed by finding an abscess by imaging study and an elevated serum antibody titre to the causative organism. Treatment for both forms of the disease is a nitroimidazole for trophozoites and a lumenal drug directed at the cysts.
In patients with diarrhoea, the finding of cysts or trophozoites is compatible with the diagnosis of giardiasis. Asymptomatically infected persons residing in endemic areas are not treated with anti-Giardia drugs since reinfection is likely. Asymptomatically infected patients in industrialised regions should be treated to prevent secondary spread. The treatment of choice for microbiologically confirmed disease and for unproven but suspected giardiasis is a nitroimidazole for older children and adults (tinidazole where approved and available) and furazolidone for infants. Single dose secnidazole appears to be a promising form of treatment for intestinal amoebiasis and giardiasis.